The invention relates to a bearing assembly for a compressor of an internal combustion engine, in particular, a bearing assembly including an angular contact ball bearing for supporting and guiding the rotor shaft of a turbocharger. Ball bearings include balls as roller bodies and an outer ring and, if necessary, an inner ring, on each of which a raceway is formed. The balls roll between the outer ring and the inner ring on the raceways and are spaced apart from each other by a cage with roller body pockets distributed around its periphery. The cage can be guided on the roller bodies or on one of the rings; in turbochargers, the guidance usually takes place on the outer ring—but it is also possible for the guidance to take place on the inner ring. The special operating conditions of a turbocharger are particular challenges when designing the bearing. The rotor shaft rotates at a rotational speed that transfers high loads into the bearing as a function of the absolute magnitude and oscillations. Turbochargers are operated at continuously changing rotational speeds that can equal at a maximum up to 300,000 revolutions per minute. In addition, high operating temperatures that act on the lubricant and the materials in use prevail, in particular, in the vicinity of the turbine wheel. Comparable operating conditions also apply to bearings for rotor shafts for compressors and so-called turbo compounds.
Typically, a rotational lock of the roller bearing cartridge is implemented by contact surfaces that are formed on a housing and the bearing outer ring. The axial locking is typically realized by a stop on the outer ends of the outer bearing sleeve. In such variants, the support in the axial direction is realized at two different positions on the housing. This involves increasing the axial play for heating the components due to different coefficients of thermal expansion. The housing can be made, namely from lightweight metal, such as aluminum or an aluminum alloy, while the bearing sleeves are made, in particular, from steel or a steel alloy.
EP 2 299 066 A1 shows, as an example, a bearing assembly for a compressor of an internal combustion engine. Shown is a bearing assembly with an outer ring of a bearing cartridge and with a positioning component that is mounted on a housing and contacts the end surface of the outer ring. The positioning component has a central cut-out with an inner periphery. In the area of the contact surface between the positioning component and outer ring, there are two pins. The pins engage in corresponding cut-outs on the outer ring and form the rotational lock. The contact area between the positioning component and outer ring forms a one-sided axial bearing. In some applications, it has proven disadvantageous that the fit in the area of the rotational lock and the axial stop must be designed as a clearance fit with large minimum play due to the heat-related expansion of adjacent components. In some applications, this can generate noise.